Commit b5dceda1 authored by Anup Patel's avatar Anup Patel Committed by Vinod Koul

lib/raid6: Add log-of-2 table for RAID6 HW requiring disk position

The raid6_gfexp table represents {2}^n values for 0 <= n < 256. The
Linux async_tx framework pass values from raid6_gfexp as coefficients
for each source to prep_dma_pq() callback of DMA channel with PQ
capability. This creates problem for RAID6 offload engines (such as
Broadcom SBA) which take disk position (i.e. log of {2}) instead of
multiplicative cofficients from raid6_gfexp table.

This patch adds raid6_gflog table having log-of-2 value for any given
x such that 0 <= x < 256. For any given disk coefficient x, the
corresponding disk position is given by raid6_gflog[x]. The RAID6
offload engine driver can use this newly added raid6_gflog table to
get disk position from multiplicative coefficient.
Signed-off-by: default avatarAnup Patel <anup.patel@broadcom.com>
Reviewed-by: default avatarScott Branden <scott.branden@broadcom.com>
Reviewed-by: default avatarRay Jui <ray.jui@broadcom.com>
Acked-by: default avatarShaohua Li <shli@fb.com>
Signed-off-by: default avatarVinod Koul <vinod.koul@intel.com>
parent 2ea659a9
......@@ -142,6 +142,7 @@ int raid6_select_algo(void);
extern const u8 raid6_gfmul[256][256] __attribute__((aligned(256)));
extern const u8 raid6_vgfmul[256][32] __attribute__((aligned(256)));
extern const u8 raid6_gfexp[256] __attribute__((aligned(256)));
extern const u8 raid6_gflog[256] __attribute__((aligned(256)));
extern const u8 raid6_gfinv[256] __attribute__((aligned(256)));
extern const u8 raid6_gfexi[256] __attribute__((aligned(256)));
......
......@@ -125,6 +125,26 @@ int main(int argc, char *argv[])
printf("EXPORT_SYMBOL(raid6_gfexp);\n");
printf("#endif\n");
/* Compute log-of-2 table */
printf("\nconst u8 __attribute__((aligned(256)))\n"
"raid6_gflog[256] =\n" "{\n");
for (i = 0; i < 256; i += 8) {
printf("\t");
for (j = 0; j < 8; j++) {
v = 255;
for (k = 0; k < 256; k++)
if (exptbl[k] == (i + j)) {
v = k;
break;
}
printf("0x%02x,%c", v, (j == 7) ? '\n' : ' ');
}
}
printf("};\n");
printf("#ifdef __KERNEL__\n");
printf("EXPORT_SYMBOL(raid6_gflog);\n");
printf("#endif\n");
/* Compute inverse table x^-1 == x^254 */
printf("\nconst u8 __attribute__((aligned(256)))\n"
"raid6_gfinv[256] =\n" "{\n");
......
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